According to WEs, as English is becoming a global language, many different kinds of local and national varieties of English are showing up. I think that those different varieties of English can be official dialect or non-official dialect and yet with the same underlying structure. My answer to your question is that #1) When you are teaching English language in the classroom, you are also teaching its cultural background, too. They are interrelated and unseparable each other. In my opinion, culture can shape and change language. So you can facilitate learners to understand the difference between standard English and localized English. #2) We should teach standard variety English in a text book, spoken by various teacher with various sound bytes. #3)The Korean students could learn either standard variety English or officialized Konglish with the same underlying structure maybe in distant future.^^

I agree with your idea partly. But I have two questions.
Culture can shape and change language. But I think language can shape culture and change culture too. Do you agree with me ?
Do you think that Korean students need to learn standard English in the textbooks or Konglish? What about various forms of Englishes such as Chinese and Japanese English with a little different expressions or sounds? I think their Englishes reflect their cultures.
Our students don't need to learn them? I look forward to hear your opinion.

Yes, you are exactly right. Culture and language can shape and change each other. We have learned that they are interrelated. I understand Konglish has long, long way to go to be officialized. It has no dictionary. Maybe in future, someone could write one. I think everything might start from there. But I disagree with using Japanese English or Chinese English or even Konglish in our text book. Text book English in standard English and how about using officialized Konglish spoken by Korean teachers to teach??